In an exemplary 3G wireless network, a wireless device may communicate via an air interface with a base transceiver station (“BTS”) and in turn with a base station controller (“BSC”). The BSC may then be coupled with a mobile switching center (“MSC”). Further, the BSC may be coupled with a packet data serving node (“PDSN”) or other gateway, which may provide connectivity with an Internet Protocol (“IP”) network, such as the Internet or an intranet (e.g., a wireless carrier's core IP network). The wireless device may thus communicate with entities on the IP network via communication path comprising the air interface, the BTS, the BSC and the PDSN.
A properly equipped wireless device can initiate packet-data communication by sending an initiation request message over an air interface signaling channel, and via the BSC, to the MSC. Applying industry standards, the initiation request message may include a “packet data” service option code that characterizes the requested communication as packet-data communications, as compared with traditional voice communication. When the MSC receives the initiation request, it may then detect the “packet data” service option code and responsively send the message back to the BSC for handling.
In turn, when the BSC receives the initiation request from the MSC, the BSC may establish a radio link layer connection with the wireless device, by assigning the wireless device to operate on a particular traffic channel over the air interface (e.g., a fundamental traffic channel, and perhaps one or more supplemental channels). In addition, the BSC may pass the initiation request to the PDSN. The PDSN and the wireless device may then negotiate with each other to establish a data-link layer connection, typically a point-to-point session (“PPP”) over which packet data can be communicated between the wireless device and the PDSN.
The exemplary 3G wireless network may employ the Mobile IP. In order to support Mobile IP, the 3G wireless network may additionally include a home agent (“HA”). Alternatively, the HA may be integrated into the PDSN. Mobile IP provides functionality that allows a wireless device to move among BTSs that are serviced by different PDSNs without interrupting the wireless devices existing packet data session. The BTSs may be on the same 3G wireless network, or they may be on different wireless networks.
When the wireless device moves to a second BTS from a first BTS, the wireless device's data-link layer connection, such as a PPP connection, with the first PDSN might remain. The wireless device may register with a foreign agent (“FA”) for the second PDSN, which in turn may provide a “care-of” address for the wireless device to a HA for the first PDSN. Once the wireless device's registration has been updated, the HA for first PDSN continues to receive packets on behalf of the wireless device in its packet data session. Instead of sending the packets to the first BTS, the HA now forwards the packets to the wireless device's “care-of address”, which is the FA. The FA then sends the packets to the second BTS for transmission to the wireless device.
While the wireless device may move between 3G wireless networks, it may also move from a 3G wireless network to a 2G wireless network. In a 2G wireless network, the wireless device communicates with entities on the IP network via communication path comprising the air interface, the BTS, the BSC, the MSC and an Internetworking Function (“IWF”). The wireless device engages in packet data communications by forming a circuit-switched connection with the IWF. The IWF in turn converts between the circuit-switched connection with the wireless device and a packet-switched connection with a packet data network. Thus, in a 2G wireless network, the IWF serves as a bridge between the wireless device and a packet data network.
2G wireless networks do not provide a mechanism for re-registering the location of the wireless device. When a wireless device moves from a 3G wireless network to 2G wireless network, the wireless device's original packet data connection with the 3G wireless network is dropped and the wireless device establishes a new data connection with the 2G wireless network. As a consequence, any data session with wireless device has established with other devices are also dropped. They too must be reestablished. Similarly problems occur when the wireless device moves from a 2G wireless network to a 3G wireless network or when the wireless device moves between 2G wireless networks.
Therefore, there exists a need to provide an improved system and method for allowing a wireless device to move among different types of wireless networks.